This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. It is well known that as an individual ages muscle mass declines. Resistance exercise and amino acids appears to be worthwhile interventions to use in the elderly to prevent the loss in muscle mass. Recent discoveries have led to the identification of microRNAs that have the ability to repress protein synthesis. Thus, the regulation of skeletal muscle growth by microRNAs may be a novel mechanisms to explore in the aged and after resistance exercise and amino acids. Based on the current literature our general hypothesis is that microRNAs are upregulated in older skeletal muscle. We also hypothesize microRNAs to be downregulated during the recovery period of resistance exercise and amino acids ingestion in young and old skeletal muscle but this response will be greater in young skeletal muscle. We will measure basal levels of microRNA 1, 133a and 206 in young and old subjects and determine if microRNA 1, 133a and 206 are up or downregulated and differentiallyregulated in young vs. old subjects during the recovery period after a single bout of resistance exercise or essential amino acids. We will study 20 young men (18-40y) and 20 old men (60 to 85y). Muscle biopsy (~150 mg) will be used to measure mixed muscle protein synthesis, intracellular enrichment, amino acid concentration, and microRNA expression. Reductions in muscle mass can lead to an increase in fractures and falls and an accompanied loss of independence and subsequent increase in mortality. Thus it is imperative to develop interventions to prevent and/or attenuate this decline.